AN INCENDIARY PRIMING AND RELEASE MECHANISM

FOR BACKFIRING FROM AIRCRAFT

by

R. L. Ponto, D. Quintillo, P. Blhunlak and G. R. Lalt

NORTHERN FOREST RESEARCH CENTRE INFORMATION REPORT NOR-X-75

JANUARY, 1974

CANADIAN FORESTRY SERVICE DEPARTMENT OF THE ENVIRONMENT

5320 - 122 STREET EDMONTON, ALBERTA, CANADA

T6H 3S5

TABLE OF CONTENTS

ABSTRACT

INTRODUCTION. • • • • . . • • • . • • • • • • . . • . • • • • . . . . • • • . • . . . • • • . • • • • • • • • • • • 1

Operational Requirements • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 2

Safety Requirements. . ... . . ... . . . . . . . . . . . . . . . . . . . . . . . . .. . 3

INC END IAR.IES. . . . . . . • • . . • . . . • • . . . • . . . . . . . . . . . . . • . . . . . . • . . . • . • • • . • 3

DESIGN OF THE INCENDIARY PRIMING AND RELEASE MECHANISM. . . . . . . . . . 4

Frame and Drive Mechanism • • • • • • • • • • • . . • • • • • • • • • • • • • • • • 4

The Capsule Chantber..... . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . 6

The Inj ection System. . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

The Ejection System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Shield. . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

OPERATION OF THE PRIMING AND RELEASE MECHANISM • • • • • • • • • • • • • • • • • • 12

DISCUSSION. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . .. .. . .. .. . . . . . . • . • • • . 13

LITERATURE CITED. . . ..... ... . ..... . . . ... . ... ..... . . ......... ... ....... . . ... ... . ... . . . 15

Figure 1. Frame and drive assembly:

(A) leg assembly; (B) aluminum plate; (C) section of frame supporting drive mechanism; (D) section of frame supporting injection pump casing and injection needle linkage; (F) drive unit assembled; (G) drive shaft and cams. . . . . . . . . . . .. . . . . . . . . . . . . . . . . 5

Figure 2. Capsule chamber and associated parts:

(A) chamber, indexing dog and brake; (B) chamber drive gear and spindle; (C) indexing dog and brake; (D) chamber linkage; (E) chamber-top view, (F) chamber-bottom view • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • 7

Figure 3. Injection system:

(A) front view; (B) side view; (C) injection block being lifted out of casing; (D) ethylene glycol revervoir and line; (E) , (F) , (G) pump and block disassembly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figur� 4. Ejection system: (A) ejection gate and linkage; (I) ejection drop tube; (C) ejection gate -closed position; (D) ejection gate - open posit ion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10

Figure 5. Shield constructed of 14 gauge sheet metal • • • • • • • • • • • • 11

Figure 6. Operator rotates drive handle and places capsules in chamber where they are subjected to injection and ejection stages . • . . . . • . • . . • • • . • . . . • . . . . • . . . . . . . . . • 12

Appendix I. Explanation of photo and blueprint number 'c:.odin.g. . . . • • . • • • • . . • . • • • • . • • • • • . • . . • . . . . . . • • . • . • • • • • 17

control.

release mechanism was utilized to

Photo - G. R. Lait

ype mounted in ldf ire under

An Incendiary Priming and Release Mechanism

for Backfiring from Aircraft

by

R. L. Pontol, D. Qutntillol, P. Bthunlakl and G. R. Latt2

Abstruat

Forest fire suppression personne 1., in Northern Canada are

presentty modifYing backfiring teahniques for aombating targe uritdfires

in remote areas. To overaome p�btems assoaiated urith ground ignition,

equipment has been dEvetoped and tested for igniting baakfires from

airaraft. This report dEsaribes the design and operation of the

inaendiary priming and retease meahanism used for aerial, ignition in

Northern Canada sinae 1.,972.

1

2

Fire Research Technician, Fire Research Officer, and Electronics Technician, respectively, Northern Forest Research Centre, Canadian Forestry Service, Environment Canada, 5320 - 122 Street, Edmonton, Alberta. T6H 3S5

Fire Research Technician, Pacific Forest Research Centre, Victoria, B.C.

- 1 -

Introduotion

Much of Canada's protected forest is accessible only by air.

Lack of equipment and personnel, and mounting costs make many traditional

fire suppression methods impractical in these remote areas. Priority

zones and maximum expenditures per fire have been established in some

northern regions to identify low value areas and provide some suppression

guidelines. Less costly suppression methods must be adopted to meet

basic requirements and maintain effective sup�ression programs.

Backfiring is an inexpensive suppression method, however its

use is limited when ignition must be carried out by ground crews. Timing

and duration of ignition frequently determines degree of success. Most

backfiring is carried out during periods of low to moderate fire danger

with the aim of burning all flammable fuels within the control lines

before high burning conditions recur. Lack of equipment and manpower,

risk to personnel, limited speed and other problems associated with

ground ignition often curb chances to backfire or cause delays reSUlting

in backfiring under difficult conditions.

The Australians have employed aerial ignition techniques

(from both fixed-wing aircraft and helicopters) on very large controlled

burning programs for several years (Packham, D. R. and G. B. Peet, 1967).

Results suggested that the technique could have value for backfiring,

however, cost of the Australian automatic priming and release mechanism

would prohibit the quantity required for wide spread emergency use on

short notice.

The Canadian ?orestry Service and the Yukon Forest Service

initiated a program in 1972 to develop techniques and equipment for

- 2 -

backfiring from the air. First suitable incendiaries were tested; then

a priming and release mechanism was designed and constructed. Lait and

Taylor's (1972) description of aerial ignition stimulated interest in

the technique's potential not only for backfiring3 but also for

burning-out4 and igniting controlled burns.

Further tests were conducted during the 1973 fire season in

the Northwest Territories, Canada. Objectives were to: (1) assess and

improve the priming and release mechanism; (2) pro�ide suppression

agencies with the design of an acceptable mechanism readily built from

blueprints. These blueprints are now available from the Northern Forest

Research Centre upon request.

The Australians encountered many problems during early

development of their incendiary priming and release mechanism. Our

prototype had to be designed with several operational and safety

requirements in mind to avoid such problems.

A. Operational Requirements

1. Small, durable and of minimum weight.

2. Portable and adaptable for use in helicopters used for fire

suppression.

3. Operated without causing fatigue.

4. Operable by one man.

3 An extensive fire set along the inner edge of a control line to consume fuel in the path of the forest fire and thereby halt or retard its progress.

4 Usually a less vigorous fire set inside the fireline to consume unburned fuels for the purpose of speeding up line holding and mop-up.

- 3 -

5. Variable, speed so it can be used in either helicopter or

fixed-wing aircraft.

6. Ethylene glycol reservoir large enough so refilling is not

necessary during most backfiring and burn-out operations.

7. Ethylene glycol filler cap fully accessible.

8. Injection system that will not corrode from ethylene glycol.

B. Safety Requirements - ,

1. Eliminate jamming and burning of primed capsules prior to

ejection.

2. Incorporate a system that injects the proper amount of ethylene

glycol without leaking or dripping between stages.

3. Shield protrusions and moving parts capable of causing injury.

4. Either incorporate a fire exting�isher or emphasize the need for

the operator to'have one within reach at all times.'

IncendiaPies

The most su�ab1e incendiary ponsists of a 7 dram pharmaceutical

vial containing 4.5 grams of 18-60 mesh particle size potassiUDJ

permanganat� (KMn04) , measured and placed into the vials by means rof

shell reloading powder measure. To activate the incendiaries, 1.4 cc of

ethy1ene.g1yco1 (antifreeze) is injected into the capsules e�ther

manually with a hypodermic syringe or mechanically �ith theprim�ng �d

release mechanism. Reaction times for 60-mesh particle size and the

coarser 18-mesh particle size KMn04 are approximately 15 seconds and

45 seconds, respectively. Cost per capsule is about 5 cents for 60-mesh.

partic,le size and 8 cents for 18-mesh parti�le size KMn04. Tests

- 4 -

conducted in 1912 showed a capsule will fall 300 feet in slightly over

4 seconds (Lait and Taylor).

Design of the Incendia11J Prtiming and Re l.ease Mechanism

The priming and release mechanism consists of five major parts:

the frame and drive mechanism (A); the capsule chamber (B); the injection

system (C); the ejection system (D); and the shield (E).

A. Frame and Drive Mechanism

The frame is relatively simple and can be modified to meet

personal preferences. The prototype model has four 12" legs of 1" anaJ.e . "

iron 1-1, 1-5, 1-7, 1-10 reinforced at the top and bottom with four pieces

1-2, 1-4, 1-6., 1-8 of the same material (Fig. 1 (A» • Two le.ngt�" of flat

iron (1-3, 1-9 in Fig. leA»� reinforce each end. The basic leg section

is bolted to a �-inch thick al\Dll1num plate 2-1 (Fig. l(B», which

supports the capsule chamber. Two sections of iron rod, 3-4-1 are welded

to a piece of flat iron, 3-4-0, which in turn is bolted to the al\Dll1num

plate (Figs. l(Bl,(C». Another iength of "flat iron 3-3 is used to

reinforce the top of this structure (Fig. l(C». Two lengths of flat

iron 3.;;'1,3..;.2 are"bent and fastened to the main "chive frame and the

aluminum. plate to give add.itional strength (Fig. l(C».

The �inch main drive shaft 7-1 (Fig. l(G»is held vet't:l.cally

�ntwo lengths of iron rod 3-4-1 by two �inc:1i bearings 3-4-2 (Fig. 1(')",

and two indexing collats 7-2 (Fig. 2(G» to avoid. horizontal movllllmlt

(Fig. leD»�. The drive handle 7";'7, 7-8 is fastened to the ahaft with

two set screws. Cams for activating the injection pump 1-6, injection

needle 7-5 and ejection system 7-4 are machined, positiofted with set

- 5 -

1. Frame and dr

section of frame

ection pump cas drive unit assembled;

; (B) aluminum ,nr\ny·ring drive mechanism;

ection pump casing; ection needle linkage;

drive shaft and cams.

- 6 -

screws and welded to the shaft once their proper positions are determined

(Figs. l(r).(G».

A �-inch iron plate was cut to the correct dimensions 4-2 and

bolted to the chamber table (Figs. l(B),(D». It supports the injection

block casing 6 as well as the linkage 4-1 for activating the injection

needle (Figs. l(D),(E».

B. The CaRsu1e Chamber

The capsule chamber 8-1 is constructed of 5-inch diameter round

aluminum shaft (Fig. 2(A». Six 1.315-inch diameter holes are machined in

the chamber so capsules are exposed to the various stages simultaneously.

Two dogs 8-3 located on the bottom of the chamber drives the chamber to

the correct position each time (Fig. 2(F». An indexing dog 9-1, 9-2,

9-3 and a brake dog 9-4 located on the s�de of the chamber prevents

backward movement (Figs. 2(A),(C». The capsule chamber has a brass

bushing 8-2 and is driven and supported by a brass gear and spindle

12-1-1 which protrudes through the ejection gate (Figs. 2(B),(E».

7

and associated s:

chamber drive gear

and brake; chamber 1 view; chamber-1-,ot tom

- 8 -

C. The Injection System

The injection system is constructed of materials that do not

corrode in glycol. The stainless steel glycol reservoir 10-2 having a

capacity of a little less than one quart was constructed so the filler

cap 10-3 was fully accessible (Fig. 3(D». A 1/8" outlet valve 10-1 allows

the operator to turn the glycol off when tlle mechanism is not in use

(Fig. 3(D». The glycol travels from the tank through about 15 inches of

plastic hose 10-4 to the injection pump 11-5 located .in the injection

breech block 11-8 (Figs. 3(A),(B),(C),(D».

The pump case, constructed of brass, contains a stainless steel

piston 11-1 (Fig. 3(G» . A stainless steel indexing sleeve. 11-2 and

trigger sleeve 11-3 at the upper end of the plunger connects the linkage

frODi the drive cam (Figs . 3(F), (G» • Two neoprene "0" rings located at

the bottom of the plunger provide a liquid-tight fit. The needle 11-6 is

stainl,ess steel surgical tubing. Coil springs 11-7, 11-4 return the

injection needle and piston to their original positions once the capsule

has been primed (Figs. 3(F),(G».

Figure 3.

- 9 -

front view; out of ca

pump and block

side (C) injection reservoir

- 10 -

D.

The al uminum ection 12-1 . 4(A),(C),(D)), located

direct under the HCl.'.UIJ<O>-, is activated same cam as the

rotary chamber. The is constructed of square iron 12-5 and a

of carburetor j 4(A)). About 24

inches of 1 3/4-inch seamless to the drop tube

13 (Fig. 4(B)) so the capsules clear the

Figure 4. Ejection tube;

gate - open

undercarriage.

and linkage; (B) - closed ; (D)

ection ection

- 11 -

E. Shield

The shield can be constructed of any

sheet metal as long as all and

injury or damaging the aircraft interior are enclosed.

aluminum sheet metal was used for the Holes were cut for:

the drive handle ; the filler cap and the (C) •

Figure 5. Shield constructed of gauge sheet metal.

Operation Re

The mechanism has been used from several hel (Bell

47G-3B-2, Bell 206A, Alouette II, Sikorski without alterations,

to either the machine or the It is bolted or c lamped (using

C clamp s) directly over the hatch where the can direct the

pilot and operate the machine.

The capsules, with 4.5 grams of

permanganate, are fed hand into the

when the drive handle is turned • 6). A

injected with 1.4 cc of

penetrates the thin cap. The

through the drop tube and bursts inte

capsule moves to the injection stage.

Figure 6. Operator rotates drive handle and chamber where are stages.

chamber, \"hich rotates

is eventually

ection needle, which

is then eeted, falls

as the next

in the ejection

- 13 -

Discussion

The aerial ignition technique allows quick action during short

periods of favourable burning conditions for backfiring, burning-out and

igniting large controlled burns. Aerial ignition can be used when ground

ignition is impractical due to a lack of equi�ent and manpower, and

limited speed. It also avoids risk to ground personnel brought about by

sudden changes in the behaviour of the fire.

During field tests we encountered only one serious defect with

the present model (Fig. 6): if the capsule chamber is turned forward

manually (i.e., without using the crank) it sometimes jams, and a capsule

burns before being ejected. This should not be a problem since the

chamber need never be turned by hand, however, it is advisable to carry

a small sharp hook to pull jammed capsules from the chamber, as well as

a fire extinguisher.

Users are advised to be aware of MOT regulations which may

influence operational use of the backfire system in their particular area.

It is also urged that only capable personnel with extensive fire

behaviour experience operate the mechanism.

- 15 -

Literature Cited

Lait, G. R. and W. C. Taylor. 1973. Backfiring and Burn-out Techniques

Used in the Yukon, 1972. Northern Forest Research Centre,

Edmonton. Information Report NOR-X-43.

Packham, D. R. and G. B. Peete 1967. Developments in controlled burning

from aircraft. CSIRO, Chem. Res. La bs. Melbourne.

- 17 -

Appendix I. Erplanation of photo and blueprint number coding.

- First number represents the part number of machine.

- Second number represents the item number of part number.

- Third number represents the piece or pieces of item number.

i.e. 's:

1-7-1

I Part No. 1 Item No. 7 Piece No. 1

1-7-1, 2, etc.

I Part No. 2 Item No. 7 Piece numbers 1,2, etc.

1-7-lA & lB

I Part No. 1 Item No. 7 Piece numbers lA and 1B

Ponto, R. L., D. Quintilio, P. Bihuniak and G. R. Lait

1974 An Incendiary Priming and Release Mechanism for

Backfiring from Aircraft.

Information Report NOR-X-75 Northern Forest Research Centre, Canada, Edmonton, Alberta· T6H 355

p. 17 Environment

Ponto, R. L., D. Quintilio, P. Bihuniak and G. R. Lait

1974 An Incendiary Priming and Release Mechanism for

Backfiring from Aircraft.

Information Report NOR-X-75 Northern Forest Research Centre, Canada, Edmonton, Alberta. T6H 3 S5

p. 17

Environment

Copies of this publication (if still in stock) may be obtained from:

Information Officer Northern Forest Research Centre Canadian Forestry Service Department of the Environment 5320 - 122 Street Edmonton, Alberta, Canada T6H 355

Blueprints for Constructing an Incendiary Priming and

Release Mechanism for Backfiring from Aircraft

Blueprints 72 sheets Northern Forest Research Centre, Environment Canada, Edmonton, Alberta· T6H 355

"Blueprints for Constructing an Incendiary Priming and

Release Mechanism for Backfiring from Aircraft

Blueprints 72 sheets Northern Forest Research Centre, Environment Canada, Edmonton. Alberta. T6H 3SS

Blueprints (if still in stock) may be obtained from:

Information Officer Northern Forest Research Centre Canadian Forestry Service Department of the Environment 5320 - 122 Street Edmonton, Alberta, Canada T6H 3S5